Rod antenna



March 27, 1956 s. A. ADAMS ROD ANTENNA Filed NOV. 9. 1951 Nl J INVENTOR. Srn-sy4404ws BY hw ww ITfa/MEYJ N m INN United States Patent ROD ANTENNA Stanley A. Adams, South Haven, Mich., assignor to Standard Coil Products Co. Inc., Los Angeles, Calif., 11 carporation of Illinois Application November 9, 1951, Serial No. 255,615 7 Claims. (Cl. 343-788) resist mechanical shocks which may damage it physically and change the inductance of the unit. I

Essentially my invention contemplates supporting the ends of the ferrite rod on a base by means of a resilient mounting, the coil being wound on the ferrite rod with the majority of its turns appropriately spaced from each other to obtain a substantial approximation of the required inductance. The turns adjacent either or both ends of the rod are closely spaced and secured together. While the majority of the turns (appropriately spaced either close together or far apart to approximate the required inductance) are permanently secured on the rod so that they will not shift in location, either or both end sections of the coil are arranged so that they may be slid by an installer or operator longitudinally of the ferrite rod to obtain an accurate adjustment of the unit for inductance either at the point of manufacture or installation.

After this adjustment is obtained, the adjusted ends may then be fixed in position at the desired adjustment.

This novel arrangement whereby adjustment of the coil may be obtained in a simplified manner at the point of manufacture or installation makes possible mass production and testing techniques in the manufacture of the unit itself without the necessity for such extreme accuracy in the manufacturing process as would make the process and the coil itself far too expensive for general use.

Since the permeability of apparently identical ferrite rods may vary rather substantially over a range of as much as 30% overall and may thereafter be varied owing to mechanical shocks impinging on the ferrite rod, the combination of the adjustment which may be made at the point of installation or manufacture together with the resilient mounting of the ferrite rod to resist physical shocks makes possible a practical unit well within the range of mass production techniques and well adapted for simplified and inexpensive installation.

Ferrite rods are very brittle and susceptible to breakage on relatively weak impacts or shocks. Consequently. the resilient mounting of the ferrite rod core on an appropriate base which may be of pressed wood or laminated paper reduces this degree of breakage which is, of course, an important factor in mechanical production and delivery of such antennae.

in addition, either lateral or transverse shocks change the electrical permeability of the ferrite rod causing a corresponding change in inductance which, of course, raises severe maintenance problems during the operation of the receiver.

Since this change in permeability is large enough to cause the antenna to mistrack in radio receivers, antennae of this type despite their excellent electrical properties h v s 89 1: nt seae sl t e- The particular mounting and particular type of adjustment provided for by my invention now makes possible the utilization of this extremely high permeability material in the formation of antenna coils.

This care in preventing physical shocks which may alter the permeability of the ferrite rod and in adjusting the inductance of the coil mounted on the ferrite rod is, of course, made necessary by the well-known fact that antenna coils must present a definite and exactly predetermined impedance to a specified signal frequency.

The adjustment of the coil provided in my invention makes possible the tuning of the coil by moving certain portions thereof along the rod to obtain the desired predetermined response over the desired frequency range. The fixing of this adjustment combined with the mounting of the core or ferrite rod thereafter assures that the adjustment will be maintained.

My invention is particularly concerned with a coil having a ferrite rod core owing to the commercial availability of ferrite rods and the high permeability thereof which tremendously increases the inductive effect, while decreasing the amount of copper or other electrical conducting material needed.

My invention is, of course, applicable to other core materials, particularly in those instances where the core material is of such nature that it must be protected from physical shock and in which, of course, the inductive effect is tremendously increased.

Thus, the primary object of my invention is the provision of a novel core wound antenna coil.

Another object of my invention is the provision of a novel core wound antenna coil where the majority of the turns of the coil are secured to the core, while certain portions of the coil are made slidable along the core in order to adjust the inductance thereof.

Another object of my invention is the formation of a novel antenna coil having a core which may be affected as to permeability by physical shock and the mounting of said core in such a manner that physical shocks will be absorbed substantially before they reach the core itself.

Another object of my invention is the formation and mounting of an antenna coil on a high permeability core, portions of the antenna coil being adjustable to obtain the desired inductance and thereafter being fixed to maintain the said desired inductance, the core itself being mounted on resilient insulating members which will absorb physical shocks before they impinge on the coil itself.

The foregoing and many other objects of my invention will become apparent from the following description and drawings in which:

Figure 1 is a view in coil.

Figure 2 is a cross-sectional view showing the terminal structure for my novel antenna coil.

Figure 3 is a side view partly in crosssection of the terminal structure for my novel antenna coil.

Figure 4 is a schematic view showing one way in which my novel antenna coil may be mounted in a receiver.

Referrin to the figures, my novel antenna coil comprises a high permeability rod core 10 on which is wound the coil 12. The section of the coil from turn 12a to turn 12b is permanently and securely wound on the core 19 which, as above pointed out, is preferably a ferrite rod.

The coil 12 itself is an appropriate electrical conducting winding suitably insulated by means of a cloth or plastic cover; preferably 28 gauge copper wire with a double celanese wrap or 24 gauge copper wire with a polyethylene coating may be used although other types of wire and other types of insulation for the wire may be used in accordance with the desired inductive effect to be achieved and the range of inductance required.

perspective of my novel antenna winding segment to control ing segments as shown in Figure l.

avenue The principal section from coil 12a to 12b is fixed on the ferrite rod in any appropriate manner as, for instance, by a cement or varnish.

While the coils from turn 12a to turn 121; are here shown closely spaced to each other, they may, of course, be appropriately spaced with respect to each other farther apart or closer together in accordance with the length of the coil itself, the inductance to be achieved and the range of the inductive effect desired; and the spacing may even be variable in order to produce an accurate response characteristic over the desired frequency range.

The turns of coil 12 which form sections 12c and 12d of the coil are not secured directly to the core 10 but may be longitudinally slidable thereon. These turns 12c and 12d are bonded together either by electrical current fusing or by a suitable cement and serve as an adjusting the inductance.

The turns 12c between turns 12a and turn 12c and the turns 12 between turn 12b and turns 12s are relatively loose on the core 10 to permit either or both of the turns 12c and 12d to be slid back and forth to obtain the de sired adjustment.

In addition and preferably, prising the adjusting segments have a portion of their circumference raised to allow looping the finished wires or leads 13 and 14 of the winding underneath the adjust- This allow for a firm anchoring of the leads to prevent unraveling the coils as well as providing for easier movement of the adjusting winding.

While I have shown the adjusting winding 12c and 120! on both ends of the coil, it is obvious that in appropriate cases only one end need be adjustable with the other end fixed and that the adjusting winding may be omitted in particular cases at one end.

Preferably, however, the utilization of the adjusting windings at both ends permits a greater range of adjustment of the inductance.

In particular commercial embodiments made in accordance with this disclosure, I have found that an inductance may be adjusted over a wide range approximately plus or minus 8% by movement of either or both of the adjusting windings as the appropriate case requires.

It is obvious that moving the adjustable windings 12c and 12b close to the main body of the winding from turns 12a to turn 12]) will provide maximum inductance. Conversely, adjusting the windings 12c and 12d away from the main body of the winding will provide the minimum inductance.

After the adjustment is made, preferably at the point of actual installation, adjustment may be fixed in any appropriate manner as by placing cement on the windings 12c and 12d to secure them to the ferrite rod core 10 or by any suitable mechanical means such as a strip of tape or a wedge or the like. Where a wedge type securement is to be used between the windings 12c and 12d and the core 10, allowance must be made at the time of adjustment for any variation in inductance which may occur 2 2 the introduction of a wedge under the windings 12c or Thus, where a wedge is used, the wedge is loosely slipped under the turns 12c or 120! during adjustment and when accurate adjustment is approached, the wedge is slipped in more tightly while nevertheless permitting some adjustment to be made so that when final adjustment is reached, the slight extra movement of the Wedge required to hold the turns in place will produce no noticeable variance in the inductance.

It is also necessary as above pointed out to mount the core 10, particularly where it is a mechanically brittle core and also one thepermeability of which is affected by mechanical shocks (i. e., a ferrite rod) in such manner that mechanical shocks will be absorbed before they reach the core itself.

the turns 12c and 12d com-' Preferably a resilient insulating sheet material of sub stantial mechanical strength in addition to its resilience is used. One example of this material is the kind of insulating paper known generally in the industry as Armite.

In the form shown in Fig. l, the mechanical supports and 21 are formed so that they each have a smooth curve at 22 which enables the units 2%) and 21 to utilize the full resilience of the material.

One end 24 of the support is secured in any suitable manner as by the rivet 23 in surface to surface relation with the insulating mounting base 25. The insulating support 20 or 21 is then curved on the smooth curve 22 and the opposite end 27 is secured in surface to surface relation with the base by the rivet 28 passing through a lateral extension 30 of the support member 26).

A circular opening 32 i of curve 22 facing inwardly toward the center of the longitudinal axis of the base and hence inwardly toward the coil which is to be supported. Since the core 1% on each side is captured in this circular opening 32 in each sup= port 2% and 21 and since owing to the curvature 22a the circular opening 32 intersects the axis of the core 10 at an angle less than perpendicular to the axis, a tight frictional engagement of the ferrite rod core 10 is achieved at each opening 32 serving to maintain the ferrite rod 10 in posi tion. This i particularly true where the circular opening 32 is made only slightly larger in diameter than the true diameter of the core 10.

The material of the support 20 or 21 as the case may be is flexed slightly at the periphery of opening 32 on each side to allow for the introduction of the core 10 and the opening 32 is made only sufliciently larger than the core it? so that the flexing which occurs will not reach the tear point of the insulating paper forming the support Ztl or 21 or the break point of the ferrite rod 10.

Preferably, minimum clearance is provided between each end of the core 10 and the outer portion 22b of the curve 22 of the support 20 or 21 as the case may be so that possible sliding of the core 10 under mechanical shock will be reduced to a minimum or obviated all together. Such sliding should not occur, however, owing to the tight frictional engagement at the opening 32 with the core 10 for the reasons above pointed out.

Since the material forming the support 20 or 21 is resilient, the smooth curve 22 provides a resiliently flexible element which in turn acts as an efiicient shock absorber for the ferrite rod 10, thereby preventing the transmission of physical shocks to the core 10 which may force it to break or to change its permeability.

Obviously, shocks or vibrations in a plane perpendicular to the base 25 will be absorbed by the resilience of the spring curve 22. Shocks or vibrations in a plane parallel to the base 25 will be absorbed by reason of the fact that rivet 23 which secures the end 27 of the support to the base 25 is offset in extension 30 which is laterally displaced from the main axis of the support 20 or 21.

Only one rivet is used in extension 30 and only one rivet is used in section 24 of the support, and the support may, therefore, yield resiliently in a plane parallel to the base 25, the yielding in one direction resulting in rotation of corner of the support member about the rivet 28 in one sense and corresponding lateral twisting of the support 20 or 21 as the case may be and the yielding in the other direction resulting in a twisting or movement of the corner 40 of the support and the other elements in the opposite sense.

For this purpose, while the rivets 28 and 28 securely hold the support elements in position, they nevertheless are so arranged that the elements of the support may rotate with respect thereto.

Where the material forming the support is so arranged that the cross-section thereof through the curve 22 is relatively narrow, then the ends of the support may be anchored securely owing to the fact that the modulus of provided in the region 22::

elasticity of a narrow section would be less to permit the lateral resilience, above, set forth to occur.

Where, however, for relative compactness a relatively short curve is to be used which, therefore, has a relatively wider transverse dimension, the rotation of the ends of the support about, the securing rivets and especially the offsetting of the securing rivets with respect to each other so that the line connecting the rivets runs at an angle to the axis of the core permits substantial lateral resilience.

By this means, therefore, the mounting is made resilient in planes atright angles to each other. Any force or shock impinging on the base will necessarily have components in a plane perpendicular to the base and a plane parallel to the base, and these components of the impinging force or shock will be absorbed by the resilience of the supports.

The leads 13 and 14 are brought out to the insulating plate secured in, any appropriate manner and carried by the reentrantly bent bracket member 52. Bracket member 52 has a section 52a which is thereby secured to the top of plate 50 and a section 52b secured to the base 2.5; the reentrant bend of the bracket 52 thus su ports the insulating plate 50 above the base 25.

Terminal clips and 61 are secured on opposite edges of the plate 50. Terminal clips 60 and 61 have a U- shaped chanel member 62, the upper leg of which is riveted at 63 to the plate 50. The terminal element 65 is cut and bent up from the clip 61. Terminal element 65a is secured in any suitable manner as by solder to the terminal clip 69. The leads 13 and 14 are soldered to terminal clips 60 and 61. Appropriate connection to the radio circuit may then be made from terminal elements 65 and 65a.

The lower leg of terminal clip 61 is angularly bent to form the spring leg 70. The lower leg of the U- shaped channel 62 on clip 60 is angularly bent to form the angular extension 71. This leg is secured in any appropriate manner as by the rivet 63a which secures the clip 60 in position to the plate on the inside of insulating plate 50. Extension 71 has an insulating extension 72 secured thereover, the insulating extension being formed of mica and extending beyond leg 71 into engagement with leg 7 0.

Since leg is resilient, it is biased away from leg 71. The adjusting screw 80, the head of which is accessible through opening 81 in base 25, passes through an opening in extension 70 and is in threaded engagement with washer 93 of plate 50. An insulated washer 94 is captured between the head of the screw and plate 7! The extension 71 is cut out so that it does not engage the screw.

Rotation of screw 80 in one direction will drive the washer 94 up to bring the leg 70 closer to the insulated leg 71. Rotation in the opposite direction will increase the spacing between the two legs. The opening in leg 70 is wide enough to receive the screw without contacting it,

by a mica washer 95.

Since the extensions 70 and 71 are insulated from each other by insulating sheet parallels the inductor.

Rotation of screw 80 by varying the spacing between plates 70 and 71 varies the capacitance across the inductor and thereby provides another tuning adjustment operable in the field.

Where the trimmer capacitor structure is not required or is replaced by some structure within the set, then the natural leads 13 and 14 may be cut to the length desired by the manufacturer of the radio set and supplied to the manufacturer in such manner that the base 25 may be supported on wall (Figure 4) of set 101 in housing 132 and the leads 13 and 14 connected in any suitable manner to connectors or terminals 104 and 104 on the chassis 106 of the set. The typing or looping of the ends of windings 12c and 12d makes this possible since the extension of leads 13 and 14 directly to or into-the, set canot result in unwinding of the coils. In this way, the need for special soldering of connecting wires or leads is obviated.

In addition, where a trimmer capacitor is not to be mounted on the base 25, and connectors such as lugs or tie points are nevertheless to be used, instead of the natural leads, then these connectors, lugs or tie points may be located anywhere on the base.

Essentially my invention as above pointed out is directed to the adjustability of the winding on the ferrite core in order to permit a field adjustment of the inductance, as Well as to provide means of adjustment at point of manufacture and, therefore, to obtain a predetermined frequency response as well as to the shock absorbing resilient mounting of the ferrite core so that mechanical shocks which may break or change the permeability of the core will not reach the core itself.

In the foregoing I have described my invention solely in connection with specific illustrative embodiments thereof. Since many variations and modifications of my invention will now be obvious to those skilled in the art, I prefer to be bound not by the specific disclosures herein contained but only by the appended claims.

I claim:

1. An antenna coil comprising a permeable longitudinal core; a winding on said core; a base; a resilient mount on said base at each end of said core; each resilient mount having resilient compliance in a plane parallel to said base and in a plane normal to said base and comprising a loop of sheet material of resilient composition; means on each loop for receiving and supporting an end of said core spaced from said base, the opposite ends of each loop being secured to said base at points on a line at an angle to the axis of the longitudinal core.

2. An antenna coil comprising a permeable longitudinal core; a winding on said core; a base; a resilient mount on said base at each end of said core; each resilient mount having resilient compliance in a plane parallel to said base and in a plane normal to said base and comprising a loop of sheet material of resilient composition; means on each loop for receiving and supporting an end of said the loop being resiliently twistable in a plane parallel to said base about said securement points and being resiliently bendable in a plane normal to said base.

3. An antenna coil comprising a permeable longitudinal core; a winding on said core; a base; a resilient mount on said base at each end of said core; each resilient mount comprising a loop of resilient sheet material forming a smooth curved section terminating with two end sections parallel to said base to provide resilient compliance in in a plane normal to said base; said loops being arranged so that similar curved surfaces thereof face each other; an opening in each loop in the curved surface thereof facing the other loop; each opening receiving and frietionally retaining an end of the core.

4. An inductor unit comprising a cylindrical core; a base; a copper winding wound on said cylindrical core; and two resilient mounts attached to said base;

end; said protruding arm and straight end being the portions of said mount attached to said base at each end of said resilient loop.

5. An inductor unit comprising a cylindrical core; a base; a copper winding wound on said cylindrical core; and rigidly attached to said base; said cylindrical core being of high permeable material and supported by said resilient mounts; each of said resilient mounts having a resilient loop for absorbing any shocks on said inductor unit; said resilient mounts each having a protruding arm and a straight end; said protruding arm and straight end being the portions of said mount attached to said base at each end of said resilient loop; said winding having a loose wound central portion and at least one close wound end portion; said central portion being fixed to said core and said end portion being slidable with respect to said core to vary the total efiective inductance.

6. An antenna coil comprising a permeable longitudinal core; a winding on said core; a base; a resilient mount on said base at each end of said core; each resilient mount comprising a loop of resilient sheet material forming a smooth curved section terminating with two end sections parallel to said base to provide resilient compliance in a plane parallel to said base and in a plane normal to said base; a portion of said winding being fixed on said core and a portion or said winding being slidable on said core toward and away from said fixed winding to vary the inductance of said antenna coil; 3. pair of leads extending from the ends of the winding; a connector mounted on said base having a pair of terminals insulated from each other, a capacitance between said terminals; each lead being connected to a terminal, said capacitance comprisiii) ing a pair of plates adjustable with respect to each other.

7. An antenna coil comprising a permeable longitudinal core; a winding on said core; a base; a resilient mount on said base at each end of said core; each resilient mount comprising a loop of resilient sheet material forming a smooth curved section terminating with two end sections parallel to said base to provide resilient compliance in a plane parallel to said base and in a plane normal to said base; a portion of said winding being fixed on said core and a portion of said Winding being slidable on said core toward and away from said fixed winding to vary the inductance of said antenna coil, a pair of leads extending from the ends of the winding; the lead extending from the slidable portion of said winding being reentrantly looped inside and through said winding.

References Cited in the file of this patent UNITED STATES PATENTS 965,065 Beck July 19, 1910 2,143,658 Morris et al. Jan. 10, 1935 2,272,433 Schaper Feb. 10, 1942 2,422,458 Amy et al. June 17, 1947 2,432,514 Depp et al Dec. 16, 1947 2,558,487 Hills June 26, 1951 

